if the service has been performed and accepted, it must also be paid.
But who was commissioned? And with what? Perhaps the client has already paid for the service -- to his construction company. They do not pay the electrician, who is now trying after 2.5 years in another place.
Just a question: GC/CM/BT? How were other additional services commissioned, accepted, paid?
It's about various things that I ordered directly from the construction company back then
Do individual items appear on the electrician's invoice? Then you remove the relevant items, recalculate the total, and pay the man with the note that you did not commission the rest from him. If the electrician issues a flat-rate invoice, you reject it with the note that he can gladly break down his total.